A)

For nozzle reinforcement calculation, required thickness of shell “tr = required thickness of a seamless shell based on the circumferential stress” as per cl. UG-37 (a) of ASME Sec. VIII Div-1. Usually for normal vessel, longitudinal stress is half of circumferential stress and hence above is OK. However, for long column where the thickness is governed by combined loading (wind/ seismic), means longitudinal stress (stress due to internal pressure + wind/ seismic loading) is more than circumferential stress (due to internal pressure), do we have to take “tr = required thickness of a seamless shell based on the longitudinal stress ” for Nozzle reinforcement calculation?
Interesting question, easy answer: Read UG-22.
All loads shall be considered. It is the responsibility of the designer to consider other stress than those of pressure which are rled by the formulae in the Code. Read FOREWORD as well ....."The Code is not an handbook and cannot replace education, experience and the use of engineering judgement" Mauro
Mauro



B)

We have designed a long column in Compress and noticed that compress takes “tr = required thickness of a seamless shell based on the circumferential stress” only for Reinforcement area requirement for Nozzle even if required thickness of shell is governed by longitudinal stress (stress due to internal pressure + wind/ seismic loading). In Compress calculation, area provided for reinforcement with Pad is passing with this approach.



However, for the same case, we have received calculation from our Column Vendor (using different design software), where in different approach is followed. Means thickness required due to combined loading is taken in to account while calculation of Reinforcement area requirement for Nozzle. Warning message is “The longitudinal stress governs over the Hoop stress on the shell course where this nozzle is located. The max stress ratio times the shell thickness will be used in the calculation of the area required”. In vendor calculation, area provided for reinforcement with Pad is not sufficient with this approach.



We kindly request you to guide us whether Compress approach for Nozzle reinforcement for long column as mentioned above is OK or calculation performed by Vendor is correct?





Kindly reply for both the above points A) & B).



We will be grateful to you if any one can reply by (before 09.04.2008).